1. Field of the Invention
This invention relates to apparatus for filling vehicle tires with a reactive liquid elastomer which when cured within the tire forms a deflation-proof elastomeric filler.
2. Description of the Prior Art
Liquids, such as polyurethane elastomers combined with suitable reactants, have been developed which when injected into a pneumatic vehicle tire will cure into an elastomeric mass providing substantially the resilient qualities of air but resulting in a deflation-proof tire. Such tires are particularly desirable for use on vehicles operating under severe road conditions or where punctured pneumatic tires would present difficult "downtime" problems. Farm vehicles, industrial vehicles, military vehicles, tractors, etc., for use in either on-road or off-road service fall in this category. Also, bicycles, motorcycles, etc., which do not normally carry spare tires benefit from the use of such elastomeric filled tires.
Examples of liquid filling materials suitable for the above purpose are disclosed in U.S. Pat. Nos. 3,112,785; 3,181,735; 3,605,848; and 3,866,651.
Although elastomeric filling materials of the above type are generally satisfactory, difficulties have been encountered in properly injecting the same into the tires. For example, in the case of tubeless tires, the tube bead must be properly set on the tire rim prior to injection of the liquid or leakage will occur which is not only wasteful but requires tedious clean up. In the case of tube tires, the tube must be properly filled out and in contact with the inner wall of the tire casing. In addition, the tire pressure should remain substantially the same throughout the tire filling operation. Also, all residual air must finally be removed from the tire to eliminate air pockets in the elastomeric filler. Further, since the liquid elastomer has a much greater viscosity than air, it is difficult and time consuming to inject the same into the tire through the usual tire valve.
Heretofore, attempts were made to maintain a constant air pressure during the tire filling operation by inserting a hollow needle in the tire and then attempting to maintain the proper air pressure by controlling release of the air through the needle with one's finger as the liquid was being injected. Obviously, this is very inexact and could result in a dangerous blow-out of the tire if the operator allowed the tire to be overinflated. On the other hand, if the operator did not maintain sufficient air pressure, the tire beads, in the case of tubeless tires, could become unseated from the rim or, in the case of tube tires, the tube could collapse from the tire wall.